Photodynamic therapy of lung cancer

Abstract

Photodynamic therapy (PDT) has been used investigationally for the treatment of lung cancer since 1980. Following systemic administration of a photosensitizing agent such as porfimer sodium (Photofrin; manufactured by Lederle Parenterals, Carolina, Puerto Rico, under license from Quadra Logic Technologies, Inc, Vancouver, British Columbia, Canada), specialized optical delivery systems are engaged to deliver light of a specific wavelength (630 nm for porfimer sodium) to neoplastic tissue. A promising use of PDT appears to be treatment of early stage lung carcinoma. Phase I-II clinical trials by Hayata's group in Japan showed that for superficial early lung cancer less than 1 cm in surface diameter, complete eradication can be achieved in approximately 90% of cases. Additional phase II-III clinical trials have demonstrated an average of 90% complete response rates for superficial tumors less than 1 cm in diameter. Preoperative PDT may be useful for larger neoplasms to reduce tumor burden and potentially lessen the degree of surgery required. At the British Columbia Cancer Agency, 22 patients with 30 radiologically occult cancers were treated with PDT. In contrast to Hayata's studies, most of these patients had rather extensive tumor burden. Thirty percent of the tumors involved two or more bronchi, and more than half of them were greater than 1 cm in surface diameter. Twenty-three percent of the cases were bronchial stump recurrences. In the group of patients with bronchial stump recurrence, although a complete response was obtained with PDT initially, local recurrences occurred in 75% of cases. These results suggest that recurrent tumor in the bronchial stump should not be treated with PDT because of difficulty in delivering light endobronchially to distal tissues. Photodynamic therapy may have a role in the palliation of advanced, inoperable, obstructive bronchial tumors. Phytodynamic therapy in combination with external radiotherapy may produce better local control than external radiotherapy alone in patients with obstructive bronchial cancers. Photodynamic therapy and conventional Nd:YAG laser therapy appear to be equally effective in relieving intraluminal obstruction by tumor. An advantage of PDT for this purpose is longer time to treatment failure; a disadvantage is photosensitization that usually occurs for up to 4 weeks after treatment. In summary, PDT is a promising curative treatment for patients with small early bronchial cancers.